2008 SUZUKI SWIFT low pressure

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On-Board Diagnostic System DescriptionS7RS0B7221007
NOTE
The diagnostic information as diagnostic
trouble code (DTC) can be known by using
SUZUKI scan tool. For further details, refer to
“DTC Check”.

HVAC control module detect s malfunctions, which may
occur in the following area.
• Outside air temperature sensor
• Inside air temperature sensor
• Evaporator temperature sensor
• Sunload sensor
• ECT sensor
• Temperature control actuator of HVAC unit
• Air flow control actuator of HVAC unit
• A/C refrigerant pressure sensor • HVAC control module
• VSS
• Serial Communication line
• CAN communication line
When HVAC control module detects malfunction, the
“AUTO” indicator lamp (1) flashes to warn and the
diagnostic trouble code (DTC) is stored in the memory of
the module. When diagnosing trouble, the DTC can be
checked according to “DTC Check”.
Schematic and Routing Diagram
Major Components of A/C SystemS7RS0B7222001
Refer to “Major Components of A/C System”.
1
I5RS0A722003-01

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Diagnostic Information and Procedures
A/C System Symptom DiagnosisS7RS0B7224001
4. Rear defogger relay 15. Evaporator temperature sensor 26. Radiator cooling fan relay No.1 37. Rear defogger switch
5. Rear defogger 16. Sunload sensor 27. Radiator cooling fan relay No.2 38. To BCM
6. Blower motor relay 17. Junction block assembly 28. Radiator cooling fan relay No.3 39. To ECM
7. Blower motor 18. ECM 29. Information display 40. To main relay
8. Blower motor controller 19. ECT sensor 30. Lighting switch 41. To main fuse
9. DLC 20. Radiator cooling fan motor 31. A/C switch 42. Back-light
10. Air intake actuator 21. Compressor relay 32. MODE (air flow) selector 43. Defroster indicator 11. Air flow control actuator 22. Compressor 33. Air intake selector 44. Rear defogger indicator
Condition Possible cause Correction / Reference Item
No cool air comes out (A/
C system does not
operate) No refrigerant
Perform recovery, evacuation and charge
referring to “Operation Procedure for
Refrigerant Charge”.
Fuse blown Check related fuses, and then check for short
circuit to ground.
A/C switch faulty Check A/C switch referring to “Inspection of
HVAC Control Module and Its Circuit”.
Evaporator temperature sensor faulty Check evaporator temperature sensor
referring to “Evaporator Thermistor
(Evaporator Temperature Sensor) Inspection”.
A/C refrigerant pressure sensor faulty Check A/C refrigerant pressure sensor
referring to “A/C Refrigerant Pressure Sensor
and Its Circuit Inspection”.
Wiring or grounding faulty Repair as necessary.
ECT sensor faulty Check ECT sensor referring to “ECT Sensor
Inspection in Section 1C”.
ECM faulty Check ECM referring to “A/C System
Inspection at ECM”.
HVAC control module faulty Check HVAC control module referring to
“Inspection of HVAC Control Module and Its
Circuit”.
Magnet clutch faulty Check magnet clutch. Referring to “Magnet
Clutch Inspection”.
Compressor drive belt loosened or
broken Adjust or replace drive belt.
Compressor faulty Check compressor.
Compressor relay faulty Check compressor relay referring to
“Compressor Relay Inspection”.
Temperature selector, blower speed
selector, and/or air flow selector faulty Check HVAC control module referring to
“Inspection of HVAC Control Module and Its
Circuit”.
BCM faulty Check BCM referring to “Inspection of BCM
and its Circuits in Section 10B”.

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3) Light over sunload sensor vertically with an incandescent lamp approximately 100 W apart from
about 100 mm (3.94 in.).
NOTE
If sunload sensor is not lighted over with an
incandescent lamp, DTC B1504 is detected
as current DTC even though there is not any
malfunction.

4) Turn ignition switch to ON position.
5) Erase DTC according to instructions displayed on SUZUKI scan tool.
NOTE
To know how to use SUZUKI scan tool, refer
to operator’s manual for SUZUKI scan tool.

6) After completing the clearance, turn ignition switch to OFF position, and then di sconnect SUZUKI scan
tool from DLC.
Not Using SUZUKI Scan Tool 1) Turn ignition switch to ON position.
2) Set temperature selector to 25 °C (77 °F). 3) Push AUTO switch (1) and
MODE (air flow) selector
(2) at the same time to have history DTC displayed.
4) Push MODE (air flow) selector (2) and OFF switch (3) at the same time while history DTC is displayed.
5) Check that “CL” (4) appears on display. “CL” means that DTC has been cleared.
DTC TableS7RS0B7224005
CAUTION!
Be sure to perform “Air Conditioning Sy stem Check” before starting diagnosis.

1
2
3
2
4
I5RS0A722008-01
DTC No.
(displayed on
SUZUKI
scan tool) DTC
(indicated on
display of HVAC
control
module) Priority of
display
(current DTC) Priority
of
display
(history DTC) Diagnosis
“AUTO”
indicator lamp
) B1502 21 1 1 Inside air temperature sensor and/or its
circuit malfunction Open
Flashed
22 2 2 Short
) B1503 31 3 3 Evaporator temperature sensor and/or its
circuit malfunction Open
Flashed
32 4 4 Short
) B1504 41 21 — Sunload sensor and/or its circuit
malfunction Open —
42 5 5 Short Flashed
) B1511 61 6 6 Temperature control actuator (position
sensor) and/or its circuit malfunction Open
Flashed
62 7 7 Short
) B1512 71 8 8 Air flow control actuator (position sensor)
and/or its circuit malfunction Open
Flashed
72 9 9 Short
) B1513 63 10 10 Temperature control actuator and/or its circuit malfunction Flashed
) B1514 73 11 11 Air flow control actuator and/or its circuit malfunction Flashed
) B1541 E1 12 — HVAC control module back-up power supply malfunction —
) B1546 d5 22 — A/C refrigerant pressure malfunction —
) B1551 91 13 12
Serial communication circuit malfunction Open
Flashed
92 14 13 Short
) B1552 94 15 14 Serial communication signal malfunction Flashed
) B1553 A4 16 15 CAN communication signal malfunction Flashed
) B1557 b4 19 16 Vehicle speed sensor signal malfunction —
) B1561 54 17 17 Engine coolant temperature sensor signal malfunction Flashed

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NOTE
When no current DTC is detected, all contents displayed on display (1) of HVAC control module and
defroster indicator (2) flash at the same time.

Fail-Safe TableS7RS0B7224006
When any of the following malfunctions (DTCs) is detected, fail-safe mode is activated.
However, when HVAC control module detects normal ope ration of A/C system, fail-safe mode is cancelled.
)
B1562 14 18 18 Outside air temperatur e sensor signal malfunction Flashed
) B1563 d4 20 19 A/C refrigerant pressure sensor signal malfunction —
— See NOTE
below
(current DTC) ——Normal —
00 (history DTC)
DTC No.
(displayed on
SUZUKI
scan tool) DTC
(indicated on
display of HVAC
control
module) Priority of
display
(current DTC) Priority
of
display
(history DTC) Diagnosis
“AUTO”
indicator lamp
1
2
I5RS0A722009-01
DTC No.
Trouble Area Fail-Safe Operation
)
B1502 Inside air temperature sensor and/
or its circuit HVAC control module controls actu
ators assuming that inside air
temperature is 25 ° C (77 °F).
)
B1503 A/C evaporator temperature sensor
and its circuit • HVAC control module turn
s off A/C switch signal.
• HVAC control module controls actu ators assuming that evaporator
temperature is 0 ° C (32 °F).
)
B1504 Sunload sensor and/or its circuit HVAC control module controls actu
ators assuming that amount of
sunlight is 0 W/m
2.
) B1551 Serial communication circuit
HVAC control module controls actuators assuming that outside air
temperature is 20 ° C (68 °F), engine coolant temperature is 80 °C
(176 °F), and vehicle speed is 40 km/h (25 mph).
)
B1552 Serial communication circuit
)
B1553 CAN communication circuit
)
B1557 Vehicle speed sensor and/or its
circuit HVAC control module controls act
uators assuming that vehicle speed
is 40 km/h (25 mph).
)
B1561 Engine coolant temperature sensor
and/or its circuit HVAC control module controls act
uators assuming that engine coolant
temperature is 80 ° C (176 °F).
)
B1562 Outside air temperature sensor
and/or its circuit HVAC control module controls actu
ators assuming that outside air
temperature is 20 ° C (68 °F).

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Scan Tool DataS7RS0B7224007
As the data values given in the following are standard values estimated on the basis of values obtained from the
normally operation vehicles by using a scan tool, use them as reference values. Even when the vehicles are in good
condition, there may be cases where the checked values do not fall within each specifies data range. Therefore,
judgement as abnormal should not be ma de by checking with these data alone.
Scan Tool Data Condition Normal Condition / Reference
Va l u e
) TEMP CONT
SWITCH Each reference value is relative to the position of
temperature selector of HVAC control module. Max Cool, 18.5
°C (65 ° F), 19 °C (66
° C) – 31 °C (88 °F), 31.5 °C (89 °F),
Max Hot
) CABIN
TEMPERATURE Reference value is relative to in-car temperature. –6.5
°C – 57.25 ° C
(20.3 °F – 135.05 °F)
) OUTSIDE AIR TEMP Reference value is relative to outside air
temperature. –23.3
°C – 65.95 °C
(–9.94 °F – 150.71 °F)
) EVAPORATOR
TEMP Reference value is relative to temperature of
evaporator. –29.7
°C – 59.55 °C
(–21.46 °F – 139.19 °F)
) COOLANT TEMP At specified id le speed after warming up. 80 °C – 100 °C (176 ° F – 212 ° F)
) SUN LOAD Reference value depends on the situation. 0 W/m
2 – 4447.8 W/m2
)MODE CONT
SWITCH Each reference value is relative to the position of air
flow selector of HVAC control module.
AUTO, FACE, B/L, FOOT, D/F, DER
) FAN CONT SWITCH Each reference value is relative to the position of
blower speed selector of HVAC control module. AUTO, OFF, 1st, 2nd – 7th, 8th
) FAN DESIRED VOLT Reference value is relative to the position of blower
speed selector of HVAC control module. 0 – 16.0 V
) AIR MIX POS SEN Reference value is relative to the position of
temperature selector of HVAC control module. about 2.0 V (Max Hot)
about 4.0 V (Max Cool)
) MODE POS SENSOR Reference value is relative to the position of air flow
selector of HVAC control module. about 1.6 V (DEF)
about 4.0 V (VENT)
) A/C CONT SIG A/C system is ON. ON
A/C system is OFF. OFF
) BLOWER LOAD SIG Position of blower speed selector is 1st position or
more.
ON
Position of blower speed selector is OFF position. OFF
) AIR INTAKE MODE Fresh air (FRE) mode is activated. FRE
Recirculation air (REC) mode is activated. REC
AUTO mode is activated. AUTO
) REFRIGERANT
PRESSURE Engine running. A/C ON (A/C is operating)
at ambient temperature:
30
°C (86 °F) 1470 – 1770 kPa For more details,
refer to pressure of high pressure
gauge under “A/C System Performance Inspection”
A/C OFF (A/C is not
operating) at ambient
temperature: 30 °C (86
° F) and engine coolant
temperature: 90 ° – 100
° C 600 – 1000 kPa After longer than 10
min from A/C switch turned off
) A/C COMP CLUTCH Engine running. A/C switch and blower
motor switch turned ON
ON
A/C switch and/or blower
motor switch turned OFF OFF
) DFR INDICATOR Defroster indicator
lamp is lighted. ON
Defroster indicator la mp is not lighted. OFF
) VEHICLE SPEED At stop. OFF
0 km/h (0 mph)

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Scan Tool Data Definitions
TEMP CONT SWITCH (TEMPERATURE SELECTOR): Position of temperature control
selector of HVAC control module
CABIN TEMPERATURE: In-car temperature detected
by inside air temperature sensor installed in HVAC
control module
OUTSIDE AIR TEMP (OUTSIDE AIR TEMPERATURE): Outside air temperature
detected by outside air temperature sensor installed
in front bumper member
EVAPORATOR TEMP (EVAPORATOR TEMPERATURE): Temperature of air passed
through evaporator
COOLANT TEMP (ENGINE COOLANT TEMPERATURE): Engine coolant temperature
detected by engine coolant temperature sensor
SUN LOAD: Amount of sunlight detected by sunload
sensor installed on the driver side on the dashboard
MODE CONT SWITCH (MODE (AIR FLOW) SELECTOR): Position of air flow selector of HVAC
control module
FAN CONT SWITCH (BLOWER SPEED SELECTOR): Position of blower speed selector of HVAC control
module
FAN DESIRED VOLT: Voltage for blower motor AIR MIX POS SEN (TEMPERATURE CONTROL
ACTUATOR POSITI ON SENSOR): Input signal
from position sensor in temperature control actuator
MODE POS SENSOR (AIR FLOW CONTROL ACTUATOR POSITI ON SENSOR): Input signal
from position sensor in air flow control actuator
A/C CONT SIG (A/C SWITCH SIGNAL, ON or OFF): State of A/C switch
BLOWER LOAD SIG (BLO WER FAN LOAD SIGNAL,
ON or OFF): ON: Position of blower speed selector
is 1st position or more / OFF: Position of blower
speed selector is OFF position.
AIR INTAKE MODE (AUTO, FRE or REC): State of air
intake mode
REFRIGERANT PRESSURE (A/C REFRIGERANT ABSOLUTE PRESSURE): This parameter
indicates A/C refrigerant absolute pressure
calculated by ECM
A/C COMP CLUTCH (A/C COMPRESSOR MAGNET CLUTCH, ON or OFF): This parameter indicates
the state of the A/C switch
DFR INDICATOR (DEFROSTER INDICATOR LAMP, ON or OFF): State of defroster indicator lamp
VEHICLE SPEED: It is computed based on pulse
signals from vehicle speed sensor
Air Conditioning System CheckS7RS0B7224008
Step Action YesNo
1 Customer complaint analysis
1) Perform )”Customer complaint analysis”.
Was customer complaint analysis performed? Go to Step 2.
Perform customer
complaint analysis.
2 Visual inspection
1) Perform )“Visual inspection”.
Is there any faulty condition? Repair or replace
malfunction part.
Go to Step 3.
3 DTC check
1) Perform )“DTC check”.
Is there any DTC code? Go to Step 4.
Go to Step 5.
4 Troubleshooting malfunction
1) Perform ) “Troubleshooting malfunction”.
Is there any faulty condition? Repair or replace
malfunction part, and go
to Step 7.
Go to Step 5.
5 Perform A/C system symptom diagnosis
1) Inspect and repair referri ng to “A/C System Symptom
Diagnosis”.
Is there any faulty condition? Repair or replace
malfunction part, and go
to Step 7.
Go to Step 6.
6 Check for intermittent problem
1) Check for intermittent troubles referring to “Intermittent
and Poor Connection Inspection in Section 00”.
Is there any faulty condition? Repair or replace
malfunction part, and go
to Step 7.
Go to Step 7.
7 Final confirmation test
1) Perform ) “Final confirmation test”.
Is there any malfunction code? Go to Step 4.
End.

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DTC B1546: A/C Refrigerant Pressure MalfunctionS7RS0B7224018
DTC Detecting Condition and Trouble Area
DTC Troubleshooting
DTC B1551: Serial Communication Circuit MalfunctionS7RS0B7224019
Wiring DiagramDTC detecting condition Trouble area
A/C refrigerant pressure sensor signal voltage is lower t han specified value
even though outside air temperature is higher than specified value for
specified time continuously. • Insufficient of refrigerant
• A/C refrigerant pressure sensor
• Outside air temperature sensor
• HVAC control module
Step
Action YesNo
1 A/C refrigerant pressure and outside air temperature
check
1) Connect scan tool to DLC with ignition switch turned
OFF.
2) Start engine and select “DATA LIST” mode on scan tool.
3) Check “Refrigerant Pressure” and “Outside Air Temp” varies displayed on scan tool.
Is displayed each va ries described varies in “Scan Tool
Data”? Go to Step 2.
Check the amount of
refrigerant and system
for leaks.
2 A/C system performance check
1) Check A/C system performance referring to “A/C System
Performance Inspection”.
Is check result satisfactory? Go to Step 3.
Repair or replace
defective part.
3 A/C refrigerant pressure sensor check
1) Check A/C refrigerant pressure sensor referring to “A/C
Refrigerant Pressure Sensor and Its Circuit Inspection”.
Is check result satisfactory? Go to Step 4.
A/C refrigerant pressure
sensor faulty.
4 Outside air temperature sensor check
1) Check outside air temperature sensor referring to
“Information Display (Clock) Removal and Installation in
Section 9C”.
Is check result satisfactory? HVAC control module
faulty.
Outside air temperature
sensor faulty.
YEL17812910
65 431516 14 13 12 11
G52
789101920121112
65 431718 16 15 14 13
G51
G51-7
12V
2
3
G37-11
I5RS0A722016-01
1. HVAC control module 2. BCM3. Information display

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DTC Troubleshooting
DTC B1553: CAN Communication Signal MalfunctionS7RS0B7224021
DTC Detecting Condition and Trouble Area
DTC Troubleshooting
DTC B1557: Vehicle Speed Sensor Signal MalfunctionS7RS0B7224022
DTC Detecting Condition and Trouble Area
DTC TroubleshootingStep Action Yes No
1 Serial communication signal data check
1) Connect scan tool to DLC with ignition switch turned
OFF.
2) Start engine and select “DATA LIST” mode on scan tool.
3) Check “Refrigerant Pressure”, “Vehicle Speed”, “Coolant Temp” and “Outside Air Temp” varies displayed on scan
tool.
Is displayed each va ries described varies in “Scan Tool
Data”? Intermittent trouble.
Check for intermittent
referring to “Intermittent
and Poor Connection
Inspection in Section
00”.
Go to Step 2.
2 Serial communication signal check
1) Connect connectors to BCM and HVAC control module.
2) Using oscilloscope, check that serial communication
signal is outputted referring to “Reference waveform
No.8” of “Inspection of BCM and its Circuits in Section
10B”.
Is serial communication signal outputted at “G37-11”
terminal of BCM connector? HVAC control module
faulty.
BCM (included in
junction block
assembly) faulty.
DTC detecting condition
Trouble area
HVAC control module receives error code fr om BCM continuously.• CAN communication circuit
• BCM (included in junction block assembly)
•ECM
• HVAC control module
Step Action YesNo
1 DTC check
1) Connect scan tool to DLC with ignition switch turned
OFF.
2) Check ECM and BCM for DTC.
Is there DTC(s)? Go to applicable DTC
diag. flow.
Substitute a known-
good HVAC control
module and recheck.
DTC detecting condition
Trouble area
HVAC control module receives error code from BCM continuously. • VSS circuit
• VSS
• HVAC control module
Step Action YesNo
1 DTC check
1) Connect scan tool to DLC with ignition switch turned
OFF.
2) Check ECM for DTC.
Is there DTC P0500? Go to “DTC P0480: Fan
1 (Radiator Cooling
Fan) Control Circuit in
Section 1A”.
Substitute a known-
good HVAC control
module and recheck.